1. Field of the Invention
The present invention relates, in general, to equipment for cleaning steam generators and, in particular, to an improved composite waterlance and cavity connection for use in a sludge lance to clean a steam generator such as a U-tube recirculating nuclear steam generator.
2. Description of the Related Art
In nuclear power stations, steam generators such as recirculating steam generators and once-through steam generators are used for heat exchange purposes to generate steam which drives turbines. Primary fluid is heated in the core of the nuclear reactor and passed through a bundle of tubes in the steam generator. Secondary fluid, generally water, is fed into the space surrounding the tubes and receives heat from the tubes converting the water into steam for driving the turbines. After cooling and condensation has occurred, the secondary fluid is directed back into the space around the tubes to provide a continuous steam generation cycle. Due to the constant high temperature and severe operating conditions, sludge accumulates on the lower portions of the tubes and on the tube sheet which supports the same. The sludge is mainly comprised of an iron oxide, such as magnetite, and reduces the heat transfer efficiency of the tubes as well as causing corrosion. Thus, the tubes must be cleaned periodically to remove the sludge. Various types of apparatus and methods are available to accomplish this task. The sludge build up is extremely difficult to remove and concentrated high pressure fluid streams are used to remove this sludge using a sludge lance from either a no-tube lane or annular opening of the boiler. Pressures of about 8,000-10,000 psi at the spray nozzle are normal. Due to the tight space constraints and the narrow spacing between the tubes or intertube lanes in a steam generator, the sludge lance requires a waterlance of a very narrow construction that can pass between the tubes in the inter tube lanes of the steam generator, for example, prior art methods employed some of the following sludge lances.
U.S. Pat. No. 4,980,120 entitled "Articulated Sludge Lance" and assigned to the assignee of the present invention, discloses an articulated lance for cleaning sludge located between steam generator tubes. In operation, the lance is inserted through a handhole into a lane or space between tubes in a tube bundle.
U.S. Pat. No. 5,194,217 entitled "Articulated Sludge Lance With A Movable Extension Nozzle" is also assigned to the assignee of the present invention and discloses an articulated sludge lance with a retractable movable extension nozzle.
In addition, U.S. Pat. No. 4,407,236 Schukei, et al discloses a thin strip of spring steel which enters a tube lane for sludge lance cleaning for nuclear steam generators. The forward ends of the capillary tubes located on the spring steel strips are directed downward for the jetting of fluid under high pressure.
U.S. Pat. Nos. 4,827,953 and 5,065,703 both to Lee are directed to an automated flexible lance for steam generator secondary side sludge removal. These patents disclose a flexible lance having a plurality of hollow, flexible tubes extending lengthwise along the flexible member to a front manifold. There are a plurality of nozzles at an end of the flexible members with the flexible member being configured to go into the difficult to access geometry of the steam generator.
The present invention through experience in this technology has found that it is desirable to anchor a front manifold to a fiber reinforced plastic material for construction of the waterlance which may be used in a sludge lance device as described in U.S. Pat. Nos. 4,980,120 or 5,194,217. Due to safety reasons, none of the components of the sludge lance device which includes the waterlance and the front manifold can be lost within the tight quarters and the difficult to access geometry of the steam generator. Very remote locations of a steam generator would make retrieval nearly impossible.
Thus, there is a need for an improved composite waterlance with a cavity connection design for firmly anchoring the front manifold thereto. This design should still fit within the tight space constraints between the tubes and effectively clean the tube lanes of a steam generator without losing any component of the waterlance including the front manifold within the steam generator.